1. Field of the Invention
The present invention relates to an internal combustion engine which uses several types of fuels.
2. Description of the Related Art
In recent years, in order to improve a fuel efficiency and reduce emission of an internal combustion engine, a compression ignition internal combustion engine represented by a homogeneous charge compression ignition internal combustion engine has been studied. The homogeneous charge compression ignition internal combustion engine compresses a fuel-air mixture consisting of fuel and air in a combustion chamber of the internal combustion engine to self-ignite the fuel-air mixture.
However, the homogeneous charge compression ignition internal combustion engine has a problem that the engine has a narrow stably-operatable region, because knocking easily occurs when a high load is required to the engine, and misfire easily occurs when a low load is required to the engine.
In order to solve the problem, an internal combustion engine using several types of fuels is proposed. For instance, the internal combustion engine is known which switches between homogeneous charge compression ignition combustion with the use of light oil and gasoline, and diesel combustion with the use of only the light oil, according to an operating state of the internal combustion engine (cf. Japanese Patent Laid-Open No. 2004-308423).
However, the internal combustion engine has such an inconvenience as to need to prepare each independent fuel tank and fuel supply system, because of using two types of fuels, namely, light oil and gasoline.